Disclosed is a system with multiple virtual machines passing I/O requests via a shared memory space. A flag in shared memory is set to a first state in response to a first hypervisor I/O interrupt to indicate that an I/O processing routine is active (running). I/O requests are retrieved from an I/O queue in the shared memory by the I/O processing routine. Based on an indicator that there are no I/O requests remaining in said I/O queue, the shared flag is set to a second state to indicate that the I/O processing routine is deactivated (sleeping). In response to said shared flag being in the second state, when new I/O requests are going to be made, a second hypervisor I/O interrupt is generated. In response to said shared flag being in said first state, I/O requests are inserted into the I/O queue without generating a second hypervisor I/O interrupt.